U.S. Pat. No. 4,660,639 to Visser et al. and U.S. Pat. No. Re. 33,102 to Visser et al. are each directed to an apparatus and method for removing volatile contaminants from the vadose zone of a contaminated underground area. This is accomplished by drilling a bore hole of a given diameter from the surface of the ground down through a contaminated area to a position just above the water table. A conduit or well casing, of smaller diameter than the bore hole, is inserted concentrically within the bore hole so that a ring or annular zone is defined between the wall of the bore hole and the wall of the conduit. The conduit has a perforate lower portion so that fluids can flow into the interior thereof whereas the upper portion of the conduit is imperforate. The annular zone between the perforate lower portion of the conduit and the bore hole wall is filled with a loose fluid-permeable first fill material, such as loose gravel, which extends substantially up to the upper end of the perforate lower portion of the conduit. The annular zone above the perforate lower portion of the conduit is packed with a second fill material of low permeability which is effective to impede flow of air from the ground surface downwardly toward the lower portion of the bore hole. Thus, the flow of air from above ground vertically downwardly into the conduit is minimized in order to increase the flow of the volatilized contaminate from the subsurface media into the conduit. A vacuum is applied to the upper end of the conduit so as to draw vapor of the contaminate present in the vadose zone into the lower portion of the conduit, the contaminate vapor then flowing to the upper end of the conduit from which it can be fed to other equipment for treatment, recovery or discharge. The perforate lower portion of the conduit is located in the vadose zone. When the perforate lower portion of the conduit extends into the saturated zone, no significant amount of ground water is drawn from the saturated zone into the conduit.
U.S. Pat. No. 4,730,672 to Payne, U.S. Pat. No. 4,890,673 to Payne and U.S. Pat. No. 4,945,988 to Payne et al. each disclose a method of removing volatile contaminates from the vadose layer of contaminated earth which comprise establishing a bore hole into the vadose layer which terminates above the water table. A loose pack fill, such as gravel is poured into the bore hole to a predetermined depth. A conduit such as an impermeable galvanized steel tubing is positioned in the bore hole spaced concentrically from the bore hole outer wall just above the fill material. The tubing is open at its lower end and at its upper end. The fluid permeable loose pack fill is then back filled into the bore hole to a level just above the tubing lower end as determined by the individual site soil conditions. A quantity of impermeable fill, such a bentonite or the like, is then packed above the remaining length of the tubing to the surface level with the tubing upper end extending slightly above the surface level. Each of the withdrawal wells, just described is surrounded by a multiple of air reinjection wells connected by a conduit. One or more pumps serve to draw the volatilized contaminate through the withdrawal well to the connecting conduit for collection. Residual air from the withdrawal well is urged back into the ground through the air reinjection wells to encourage further contaminant to move toward the withdrawal well for collection.
U.S. Pat. No. 4,886,119 to Bernhardt et al. is directed to a method for driving volatile impurities from the ground wherein a bore hole is provided with a central shaft whose upper end is sealed from the outside by a plate. A first non-perforated suction pipe extends in the drilling shaft to the proximate end of the shaft. A second suction pipe concentrically surrounds the first suction pipe, with a space therebetween, and extends to half the length of the drilling shaft. The inner ends of both pipes form suction locations. The ends of the suction pipes extend outside of the shaft in a fluid separating chamber. Means for drawing a vacuum is provided at the upper end of the drilling shaft. In addition, an air supply pipe extends through the closing plate so that outside air can flow into the drilling shaft. Sieve ring bodies are arranged at the ends of the suction pipes, each of which has a flexible sieve wall which can be composed of metal sieve web or synthetic plastic sieve web. The upper part of the shaft is supported by a loose aggregate material.
While each of the inventions described above fulfills its intended purpose, each structure is somewhat complex and therefore expensive to provide and requires significant labor for installation.